WyIL: working on the new bytecode API which will support nested blocks. #190
WyIL: refactored all concrete bytecode constructors and classes in class Codes.
WyIL: restructured Code hierarchy to include Code.Unit and Code.Block.
WyIL: renamed several bytecode classes in Codes.
WyIL: updated syntax in bytecode documentation.
WyIL: moving CodeBlock into Code as Code.Block.
Merge branch 'master' of github.com:DavePearce/Whiley into wyil-nested-blocks
WyIL: continued fixing bugs after refactoring CodeBlock into Code.Block.
WyIL: made some minor documentation updates.
TEST: Adding missing test case output.